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Beth Stackpole
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Back to the basics
Beth Stackpole   11/17/2011 6:38:31 AM
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Great lesson learned here in how important it is to consider all options, however small and obvious. Given how complex technology has gotten and in light of the really impressive and powerful tools engineers have at their disposal to solve complex design challenges, I think basic exploratory practices and simple design iterations are often overlooked in favor of pursing the big or overly complex idea or solution. Yet another reminder not to forgo the basics.

Rob Spiegel
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Re: Back to the basics
Rob Spiegel   11/17/2011 7:48:33 AM
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You're right, Beth. We had a similar Sherlock Ohms posting, The Case of the Mismarked Resistor, where something as simple as a resistor that had the wrong ID snafu'd a project.

Charles Murray
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Re: Back to the basics
Charles Murray   11/17/2011 9:01:26 PM
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I suppose that the lesson here is not to ignore the obvious, but I have to admit that I could have looked at that TV for a month and never have thought of the "non-magnetized magnet." Maybe that's why the author still got the job.

Alexander Wolfe
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Re: Back to the basics
Alexander Wolfe   11/18/2011 10:06:24 AM
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I don't mean to be glib, but I honestly wonder how technically oriented kids learn anything today, given that not much stuff is repairable or even analyzable anymore. When I (we; you and me both, Chuck) were young, we could tinker around with the innards of a TV or radio (often at risk of electrical shock) and learn important stuff before we even reached engineering school (which incidentally never taught me to read schematics; I learned that on my own long before, from electronics magazines).

DougM21
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Silver
Re: Back to the basics
DougM21   11/18/2011 11:19:10 AM
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"... I honestly wonder how technically oriented kids learn anything today, given that not much stuff is repairable or even analyzable anymore."

Someone gave me an old Dynaco transistor stereo preamp/amp recently, it sort of worked, but needed some simple repairs to be useful.  I didn't feel like fixing it, so gave it to a local audio repair shop--with the suggestion to give it to a kid who could have some easy success and perhaps catch the "fix it" bug.  For those not familiar with the brand, Dynaco sold kit and assembled versions, the kit manuals are still available to help a novice get started.




Ann R. Thryft
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Re: Back to the basics
Ann R. Thryft   11/18/2011 1:16:17 PM
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Not much stuff is repairable or even analyzable anymore--I'll second, or third, that comment. Remember when you could fix not only electrical and mechanical appliances, but also your car? And what about all those budding engineers taking apart the proverbial radio and other old-timey electronics? Good luck with today.

Charles Murray
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Re: Back to the basics
Charles Murray   11/18/2011 6:41:17 PM
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I suppose this has become a cliche, but electronic control has made it more difficult for kids to do the kinds of things that we used to do as kids, Alex. Engines and transmissions have powertrain controllers. Brakes are all ABS. Most components -- even down to the catalytic converter -- converse with engine management system. Then there's the issue of lack of space: On old cars we could lay underneath the car, look up and see the ceiling of the garage. Today, the FWD transaxle obliterates all light under there. The bottom line is that you can still work on your car if you're determined, but it's really hard for kids to know where to start. You have to go to school and take a class to get started, instead of just learning by dumb trial and error, as we did.

Curt Carpenter
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Gold
Re: Back to the basics
Curt Carpenter   11/18/2011 10:59:59 AM
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Beth Stackpole mentions all of our great design tools -- which made me think about the very FEW tools we have to support routine troubleshooting.  Is there a business opportunity for someone there?  (Microsoft makes a valiant effort to provide troubleshooters for it's products -- but I find they usually just add to my level of frustration!)   Here's one vote for a "Troubleshooting App" based on a "troubleshooting science."





Keith Harris
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Iron
Re: Back to the basics
Keith Harris   11/18/2011 11:24:26 AM
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I work in an environment where production runs are very short, usually only a few copies of any design.  A common problem in troubleshooting is that we are lulled into believing that the written schematic is an accurate representation of the system.  For the prototype or first article the thing to remember is: "It ain't necessarily wired the way we think it is."  This is also true for EMC problems, which don't show up in the circuit diagram.

Alexander Wolfe
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Can you hear me now?
Alexander Wolfe   11/17/2011 9:52:25 AM
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As an old analog person, I'm reminded of how one could always test one's hearing by determining whether you could hear the faint sound of the 15kHz horizontal-scan signal emanating from those old vacuum tube TVs.

BobGroh
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Platinum
Great story!
BobGroh   11/17/2011 10:00:00 AM
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Enjoyed the story of the 'Non-Magnetized TV Magnet'.  It really embodies the essense of so much of the trouble shooting that we engineers and technicians go through as we go about our daily life.  Great stuff and an enjoyable read.

Ann R. Thryft
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Re: Great story!
Ann R. Thryft   11/17/2011 12:40:46 PM
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This story and the troubleshooting process the author followed reminds me of the 101 basics I learned first on my stereo system: Is it plugged in? Is it switched on? In this case, the question is, Is the magnet magnetized?

Rob Spiegel
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Skepticism
Rob Spiegel   11/18/2011 2:38:28 PM
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It takes a deep amount of skepticism to check of the magnet is magnetized, the same kind of mind that looks both ways before crossing a one-way street. There are many cases in life where the obvious is overlooked.

Charles Murray
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Re: Skepticism
Charles Murray   11/18/2011 6:44:55 PM
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I agree, Rob. Skepticism is the right word. Checking if the magnet is manetized is roughly equivalent to opening your car's hood every morning to see if someone disconnected your battery during the night.

bdcst
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Platinum
Re: Skepticism
bdcst   12/5/2011 5:03:29 PM
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Quite often those of us who have the "knowledge" will assume the problem is of a more complex nature than it may be.  But with greater "experience" one can temper the impulse to tear into a problem without first checking on the simple and obvious.  Is it plugged in?  Are all connectors tight?  Is the lens cap off?

The other day I removed a defective device from service and substituted a recently factory repaired unit.  That did not solve the problem.  Good thing I knew there was nothing wrong with anything else external to the device through previous testing as it turned out to be dud.  A second spare worked fine.  Now, I could have decided the problem was elsewhere as the spare had been factory sealed and should have solved the problem!  Sometimes you have to be prepared for the unexpected.

Rob Spiegel
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Re: Skepticism
Rob Spiegel   12/8/2011 4:03:29 PM
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Hi BEDST,

If you could elaborate on your story and send it to me at rob.spiegel@ubm.com we could include it as a Sherlok Ohms entry. If you chose to do so, please send along a short bio as well.

William K.
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Platinum
The non magnetized magnet and troubleshooting
William K.   11/19/2011 8:07:18 PM
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I have never come across a failed magnet in an ion trap assembly.

As for getting into troubleshooting, that is something that I do not only for profit, but also for fun. I have written manuals for some of my employers products with the intention that they would save me from needing to visit some plant and repair equipment.

There are two ways to troubleshoot, the first is to check things until you find something that is not right, and the second one is to understand correctly and in detail how something works, and then look for the part that has stopped working correctly. Actually there is a third method of troubleshooting, which is to randomly replace components until the item starts working again. Of course, that method usually will not correct a problem requireing adjustment instead of replacement.

Over the years there have been a few instruments created to assist by substitution of signals. Many of these are called "Channylists", or some other spelling of the same word. The ads are always interesting, but unfortunately many of them offer little more value than a good multimeter, a circuit schematic diagram, and an understanding of how the item works.

There are things made to assist in finding the points of failure, and some of them are indeed quite useful, although many of them still demand that the service person actually understand the process of the device being serviced. So it would appear that a service career may be secure, until the quality of the products being serviced falls to the point where they are not worth fixing.

Keith Harris
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Iron
Trouble with magnets...
Keith Harris   11/21/2011 2:53:58 PM
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The discussion has called to mind an experience from the late 70's.  A system I was working on had two motor driven components (running just under 1000 rpm) and some electronic subsystems that had to be synchronized to the shaft position of each of them.  One channel was working fine, but the other was triggering erratically.  The shaft position sensor was a bar magnet attached to the rim ofa flywheel and the pickup was a simple coil to generate a pulse when the magnet flew by.  We finally (after hours of looking at connectors and cables) removed the clamp that held the magnet, and discovered that the weak signal was due to a broken magnet.  Based on the appearance of the broken ends the material was probably alnico, which is pretty brittle.  A new magnet solved the problem immediately. 

Rob Spiegel
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Blogger
Re: Trouble with magnets...
Rob Spiegel   11/21/2011 3:03:11 PM
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Hi Keith,

If you could expand on your story here, we could use it for a Sherlock posting. We try to make sure the postings are at least 300 words. You could get there by explaining some of the hits and misses as you tried before you identified the problem. We're always looking for good stories, and yours looks good.

If you're game, please send it to: rob.spiegel@ubm.com

Centrevision
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Iron
Key to diagnosis
Centrevision   11/21/2011 9:12:23 PM
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"The key to diagnosis,however,is knowledge of how the circuit is supposed to work rather than the availability of elaborate test equipment or a degree in electronics" - Eugene Trundle (Author Servicing TV And Video Equipmemt). From that comes knowing exactky what is wrong with a piece of equipment then its just a short step from having it working again,and the most succesful engineers are,(were?),those who have the aility to quickly track down,to componenet level,the root of the cause. This might sound logic or not but its always the best approach to trouble shooting.I mean,why buy a Mercedes when you dont know how to drive a car?



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